Turnagain Pass Avalanche Forecast

Snow started falling this morning and will continue to fall for most of the day today (fingers crossed we avoid the “R” word). This weather pattern is already favoring Girdwood over Turnagain. Five inches have already fallen in Girdwood with only an inch registering on the Center Ridge SNOTEL.  An additional 4-7″ is forecast to fall today. The avalanche danger will be really dependent on how much snow we get and how well it bonds to existing snow surfaces.  The winds aren’t supposed to be strong but if they kick up a bit they could add to the slab building in the Alpine. Paying attention to changing conditions will be crucial today. If this storm really produces, watch for storm slabs to form. Southerly slopes have a sun crust, northerly protected slopes have loose faceted snow and wind affected terrain has a hard wind crust. New snow is not expected to bond well to any of these surfaces.  The temperatures will also rise, potentially creating a bit of an ‘upside down’ storm situation with heavier snow falling on lighter snow. The other factor to consider is that triggering a storm slab avalanche could overload our layers of lurking buried weak snow and produce a larger avalanche (more in Problem 2).

The rain/snowline may rise to around 500′. Rain on snow may produce small roller balls and mini wet loose avalanches.

Dry loose snow avalanches: Steep slopes that have been sheltered from the wind have up to a foot of loose snow sitting on top of firm surfaces. New snow will add volume to this set-up. It will be easy to trigger dry loose avalanches (sluffs), and they could pickup enough speed to carry a person. While it is unlikely they will be big enough to bury you, they can be dangerous if they drag you into terrain traps like cliffs, trees, rocks, or gullies.

Snow surface buffet – sun crust, soft facets and hard wind affected snow. 3.24. 21

Today’s storm will cover up the existing snow surfaces, making it a bit more challenging to figure out where the old wind affected snow is. It could will also add more load and  potentially create more of a slab. Our concern continues to be finding a spot where there is a slab over the layers of buried weak snow in the upper 1-3′ of the snowpack.  This is where we think it is still possible to trigger a persistent slab avalanche. The most recent human triggered avalanches were on steep slopes with hard wind affected snow sitting on top of facets and/or surface hoar. These buried layers of weak snow seem to be widespread across the forecast area. The part that remains variable is the character of the snow resting on top of the weak snow. Figuring out whether or not there is a slab is key to safe travel in steep terrain. Be on the lookout for indications of previous wind-loading under the new snow, including stiff snow on or a hollow, ‘punchy’ feeling slab. The most suspect terrain will likely be at upper elevations, especially immediately below ridgelines, in cross-loaded gullies, and below convexities. As always, watch for signs of instability, use good travel protocol, and think about terrain consequences. This type of avalanche issue might allow you to get well out on to the slope before the avalanche releases and it might not be the first person that triggers the avalanche.

Buried surface hoar sitting under hard wind affected snow just off the ridgeline on the north side of Tincan. 3.24.21.

Another layer of buried surface hoar 2′ down in a snow pit on the north side of Tincan, 3.24.21. The results of a Propagation Saw Test indicated that there is still a possibility of triggering an avalanche on this layer.

.

We’ve heard reports of some glide cracks and failure within the advisory area.  Glide avalanche failure is difficult to predict.  Stay out from underneath them!